We report effects of applying variable doses of Holmium:YAG laser energy to bovine articular cartilage in vitro. The response of the cartilage to the Holmium:YAG laser energy was determined by quantification of cell proliferation and extracellular matrix glycosaminoglycan synthesis. This study demonstrates that articular cartilage cell metabolism was maintained at a normal level following treatment of cartilage at a dose of 0.6 joules/pulse. The laser energy was applied at 10 Hz for 10 seconds at 1 mm distance from the cartilage. Under these conditions and at a dose of 0.6 joules/pulse, the total energy density was calculated to be 240 joules/cm2, assuming minimal loss of energy due to water absorption. Energy levels grater than 0.8 joules/pulse corresponding to calculated energy densities greater than 320 joules/cm2 proved harmful to cartilage. Our data demonstrate that low levels of Holmium:YAG laser energy can be applied to articular cartilage under conditions that maintain and/or stimulate cell metabolism.